Descriptions

Two separate time series observations of light transmission in the bottom water on the Continental
Rise off Nova Scotia show fluctuations of light transmission in a wide range, 0-50% transmission at λ
= 660 nm. The range corresponds approximately to SPM concentrations of 12 mg/l to 150 μg/l. The
former is the maximum value determined by filtration (Biscaye, 1980), and the latter is determined by
an empirical relation between beam attenuation coefficient and particle volume determined by a
particle counter. Nepheloid layers of significant turbidity, called benthic storms, were observed in 30
and 10% of the time, respectively, for the two observations, and each storm lasted 2-5 days. High
frequency fluctuations represented by pulse lengths less than 10 min were observed superimposed on
the low frequency fluctuations during 16 and 4% of the time. Both the major storms and the high
frequency pulses are interpreted to be a result of resuspension of bottom sediments at varying
distances from the instrument; the high frequency pulses are thought to be a result of erosion at a
relatively short distance, while the low frequency fluctuations result from erosion at greater distance.